Crabs of the genus Trapezia, from here.

Belongs within: Heterotremata.

The Trapeziidae are a family of small crabs that live as symbionts of cnidarians, usually corals. They feed on mucus from the coral, as well as detritus and zooplankton captured by the host.

Characters (from Schwietzer 2005): Carapace cordate, not much wider than long, length averaging about 86% maximum carapace width, position of maximum width about half the distance posteriorly on carapace; carapace regions not defined; front weakly bilobed, four-lobed, serrate, or nearly straight, about half maximum carapace width; orbits deeply excavated, positioned at corners of frontal margin of carapace, directed anterolaterally, fronto-orbital width about 90% or more maximum carapace width; anterolateral margins short, usually oriented nearly perpendicular to frontal margin of carapace or oriented at very high angle to frontal margin, entire or with one or two spines; chelae unequal, smooth or weakly granular, merus of cheliped extending beyond carapace margins when folded; pereiopods 2-5 with dactylo-propodal articulation formed by rounded prolongation of propodal lateral margin sliding against and beneath a projecting button situated proximally on lateral margin of dactylus; basal antennal article slender; efferent channels defined by well-developed endostomal crests; merus of third maxilliped shorter than ischium, about as wide as long; endopod of second maxilliped composed of four separate segments; male abdomen with somites 3-5 fused with visible sutures or with all somites free.

    |--Quadrella reticualta Alcock 1898 MG-H11
    |--Hexagonalia MD01
    |--Calocarcinus MD01
    |--Philippicarcinus MD01
    |--Sphenomerides MD01
    `--Trapezia TSH09
         |--T. areolata Dana 1852 TSH09
         |--T. bidentata (Forskål 1775) TSH09
         |--T. cymodoce (Herbst 1801) TSH09
         |--T. digitalis Latreille 1828 TSH09
         |--T. guttata Rüppell 1830 TSH09
         |--T. lutea Castro 1997 TSH09
         |--T. rufopunctata (Herbst 1799) TSH09
         |--T. septata Dana 1852 TSH09
         `--T. tigrina Eydoux & Souleyet 1842 TSH09

*Type species of generic name indicated


[MD01] Martin, J. W., & G. E. Davis. 2001. An updated classification of the Recent Crustacea. Natural History Museum Los Angeles County, Science Series 39: 1–124.

[MG-H11] McEnnulty, F. R., K. L. Gowlett-Holmes, A. Williams, F. Althaus, J. Fromont, G. C. B. Poore, T. D. O'Hara, L. Marsh, P. Kott, S. Slack-Smith, P. Alderslade & M. V. Kitahara. 2011. The deepwater megabenthic invertebrates on the western continental margin of Australia (100–1100 m depths): composition, distribution and novelty. Records of the Western Australian Museum Supplement 80: 1–191.

Schweitzer, C. E. 2005. The Trapeziidae and Domeciidae (Decapoda: Brachyura: Xanthoidea) in the fossil record and a new Eocene genus from Baja California Sur, Mexico. Journal of Crustacean Biology 25 (4): 625-636.

[TSH09] Titelius, M. A., A. Sampey & C. G. Hass. 2009. Crustaceans of Mermaid (Rowley Shoals), Scott and Seringapatam Reefs, north Western Australia. Records of the Western Australian Museum Supplement 77: 145–176.

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